Apparatus for separating cooking liquor from pulp



April 15, 1952 P. G. voN HILDEBRAND-r 2,592,983

APPARATUS FOR SEPARATING COOKING LIQUOR FROM PULP original Filed July 2, 1945 4 Sheets-Sheet l A140/fry April 15, 1952 P. G. VON HILDEBRANDT APPARATUS FOR SEPARATING COOKING LIQUOR FROM PULP 4 Sheets-Sheet 2 Original Filed July 2, 1945 il .L

ttorneg 4 Sheets-Sheet 3 P. G. VON HILDEBRANDT APPARATUS FOR SEPARATING COOKING LIQUOR FROM PULP 6 INVENTOR.

BY 7940/6. ro/:A/Mdenfm/ l 1 l l April 15, 1952 Original Filed July 2, 1945 April 1,5, 1952 P. G. voN HILDEBRANDT 2,592,983

APPARATUS FOR SEPARATING COOKING LIQUOR FROM PULP original Filed July 2, 1945 4 Sheets-Sheet 4 all' ' l' lllllzlzlzlzlzlnl Patented Apr. l5, 1952 APPARATUS FOR SEPARATIN G COOKING LIQUOR FROM PULP Paul Gfvon Hildebrandt, Portland, Oreg. @riginal 4vapplication July Y2, '1945, Serial No.

602,898. Divided and this application VJuly 17, 1947, Serial No. 761,585

12 Claims.

through the pulp, thereby maintaining the resins and lignins in ay fluid condition.

A still further object of my invention is topro.- vide apparatus in which the cooking liquor is separated from pulp with ya minimum of water dilution, thereby reducing foaming and the amount of heat required for evaporating the black liquor down for subsequent burning.

A still-further object of -my invention iste provide apparatus for separatingpulp from cooking liquor, which includes means for employingsteam as the separating agent.

A more specific object of my invention is the provision oi apparatus for separating kcooking liquor from pulp, which includes a blow tank throughwhich the pulp moves continuously, having the major portion of the liquor separated therefrom while in transit, without the use of wash water, thereby minimizing foaming and the loss of pulp with the foam.

While not limited thereto, my improved process will be described in connection with the manufacture of paper 'by the sulphate or soda process. lt will be apparent, however; from the description which is to -fo'llow that it is equallya-pplicable-for use in separating pulp from cooking liquor in the sulphite process.

-Heretofore in the manufacture of paper by the sulphate or soda process, when the mi-xture -of black liquor and pulp is discharged from the `digestors, it is usually-passed to a difuseror to va pulp Vwashing machine where the black'liquor is separated from `the pulp. In dischargingA the pulp from the digestors diiculties have been encountered in the loss of pulp with the escaping steam. -Inthe diffuser type of separator, the black liquor is drained through a perforated bottom on which the pulp is retained, and weak liquor is supplied to the mass of pulp to displace and wash the stronger black liquor from the bers until the liquor has reached its minimum density. .'Hot water -is then used to continue vthe .washing of 2 the liquor from `the bers. 'In the vacuum type of pulp washing machine, there is a rotary, perforated metal cylinder covered with-a-ine-mesh wire screen which is partly submergedand rotated in amixture of pulp andblackliquor. The inner side of the cylinder is .connectedto a suction device and during a .partof `each revolution a layer of pulp is drawn Yontothe screenandithe black liquor is filtered out. During at-furtherpart of the revolution, `hot watershowers .drenchlthe mat of fiber on the ldrum kand this washpvater is also drawn through the screen. JThe :mato'f pulp is then washed off the screen withipowerful jets of water into a stock chest.

With either of these methods, zafgreatfdeal of water is employed and thexgblack` liquoris greatly diluted. As is also Well known, it is .the .practice to evaporate the black liquor downto'a Ac onsistency .where it can be economically employed ,as a fuel and then it is burnedintheboiler furnaces cf the mill Yto supply heat rand to recover the chemicals used Vin cooking ithe wood chips. .The heat required to evaporate the black liquoridown is expensiveand itis the principal object ofmy invention to .provide -a process :and v,apparatus which will recover the blackliquor withiaminimum of dilution.

In vaccord-ance with my invention, VI provide. a blow tank of the necessary `capacityto takecare of the pulp as it is cooked, .The digestorszarecdischarged into this blowtank through acyclone having a vweighted valve in the "bottomrthrough Vwhich the pulp passes.downwardlyintoL-th tank. The y.tank -is providedwith :a .perforated .screen conical bottom through Which..the'lolack`liquor drains into a storageetank. jAtthelowerend of `the conical bottom, isdisposeda screw conveyor which `removes the pulptas itlreaches the. conical bottomofzthe blow tank. The.,conveyor1is-pro vided Vwith a perforated trough through zwhich the liquor' Acontinues .to drain. While'inithe conveyor, steam `is diffused through the .pulp which maintains V`the lignins and resins ina-,liuuid;c9n ditionvso thatthey are expelled fromthefpnipfrespnsive t0 thesqueeznglactien of thecQnvei/or screw. This is very importanti-n separat-ine the black liquor ,-.from 4the knots which :practice absorbfthe greater `nreportion..ofthe black liquor. A plurality of screw conveyorsare preferablfysemployed, each of which -has an increasing :diameter from .its linlet `to vits discharge end y.thereby to allow for the `expansionofthelpulpasritis separated from the blackliquon and toproyide for better diiiusion .of the Jsteams'through the pulp. Other featuresA of my inventiongconsistef 3 means to prevent the carrying over of pulp with the steam from the black liquor as it is discharged from the digestor and in the various details of construction and arrangement of parts hereinafter described.

Apparatus embodying features of my invention is illustrated in the accompanying drawing, in which:

Fig. 1 is an assembly view showing the apparatus for carrying out my invention;

Fig. 2 is a detailed sectional view of the cyclone through which the pulp-black liquor mixture is blown into the blow tank, and taken along the line II-II of Fig. l;

Fig. 3 is a sectional view of the blow tank, and the screw conveyor connecting with the lower end of the tank;

Fig. 4 is a. view taken at right angles to Fig. 3 and showing one of the screw conveyors in secion;

Fig. 5 is a sectional view taken along the line V-V of Fig 3;

Fig. 6 is a sectional VI--VI of Fig. 3;

Fig. 'l is a sectional view showing the manifold and baille arrangement through which the steam from the black liquor is discharged;

Fig. 8 is a sectional view taken along the line VIII- VIII of Fig. 7;

Fig. 9 is a plan view of the screw conveyors;

Fig. 10 is a side elevation thereof with parts broken away;

Fig. 1l is a sectional View taken along the line XI-XI of Fig. 9; and

Fig. l2 is a sectional view typical of the three conveyers showing the means for admitting steam to the pulp.

Referring now to the drawings for a better understanding of my invention, I show in Fig. 1 a paper mill installation comprising a digester I0, a blow down line I I, connected to the digestor, and discharging into a cyclone I2. From the cyclone I2, the black liquor and pulp pass downwardly with a whirling motion into my improved blow tank I3 wherein the black liquor is separated and flows into a storage tank I4. The pulp is removed from the blow tank by means of a system of screw conveyors I6, I1 and I8.

The cyclone I2, is provided with a tangential inlet I9. and a bottom outlet 2I in which are located weighted trap valves 22 and 23 which open responsive to the weight of the mixture of pulp and black liquor on them allowing it to pass downwardly through the discharge opening 2l into the blow tank I3.

Mounted above the cylone I2 is a baille cham- .ber 24, shown in detail in Fig. 7. The baille cham ber 24 has its wall 33 provided with a multiplicity of downwardly inclined overlapping baffles 25. It is open at the bottom and top as shown in Fig. 7 and has connected to the upper end a discharge conduit 21. Steam from the pulp and black liquor being discharged from the digestor I0, passes upwardly through the baille chamber, the bailles 26 serving to intercept any pulp being carried over with the steam and to return it to the cyclone I2. There is thus no loss of pulp due to being carried over by the steam. Surrounding the baille chamber 24, is a manifold 28 having a lateral connection 29. The wall 30 is perforated as shown at 3|, within the manifold 23, whereby liquor or steam may be admitted when required through the connection 251i and pass through the perforations and over the baffles to wash and remove any accumulation of pulp thereon.

view taken along the line The blow tank I3, as shown in Fig. 3, comprises a cylindrical inner shell 33, made of steel plate which is provided with a conical bottom 34. At the bottom is an opening 36, through which the pulp is discharged. The inner shell 33, is perforated for approximately three-fourths of its height from the bottom with relatively large perforations 31. Fitting within the shell 33, are relatively thin gauge plates 38, having relatively fine perforations, forming a screen. These plates are preferably made removable by any suitable means, not shown, whereby they may be changed when required. The upper end of the inner shell 33, has connected thereto a conduit 39, leading to a safety valve 4I, for the relief of excess pressure within the inner shell. Also, at 42 is shown a conduit leading to a pressure gauge 43. After the digester is blown and the inner shell is full, pressure accumulates due to the contained heat of the liquor and pulp. This pressure aids in draining the liquor from the pulp through the screens. The connection to the cyclone I2, is made by means of a frusto-conical outlet connection 44, terminating in a flanged opening 46, which connects with the flanged outlet 2I of the cyclone. This frusto-conical connection 44 aids in distributing evenly the incoming pulp around the inner shell and in throwing out liquor. Surrounding the lower perforated portion of the inner shell 33 is an outer shell 41 having its upper end joined to the inner shell at d8, as by welding. The outer shell 41 is generally cylindrical in shape and is connected to the storage tank I4 by means of a flanged connection 4B. At 5I I show a manifold extending vertically alongside the outer shell 41, and connected to the manifold are a plurality of conduits 52, 53, 51-, 5B, 51, 53, 59, and 6I. The conduits 52, 54, 51, 53 and 6I extend through the inner shell 33, and connect to headers 62 which lie closely adjacent the inner wall of the shell 33 and are provided with downwardly directed jets 63, through which liquor, as desired, may be discharged. The conduits '53, 55 and 53 terminate in headers G4 which surround the outside of the inner shell 33, lying closely adjacent thereto, and are provided with downwardly directed jets 66.

Connected to the discharge opening 36 at the lower end of the conical bottom 3:1 is an upwardly inclined trough or jacket B1 for a screw conveyor having a tapered screw 69 which increases in diameter from the lower end where the conveyor connects to the discharge opening to its upper, discharge end. The lower half of the trough 61 is provided with perforations 1 I, through which black liquor removed from the pulp by the action of the conveyor, drains downwardly into the storage tank I4. Outside the shell 41 there is an outer housing 12, which is joined to the trough 61, at 13, above the perforations 1I. See Fig. 6. The housing 12, is connected by means of a flanged connection 14 to the outer shell 41, and communicates with the inner shell 41, through an opening 15. Inside the shell d1, the trough 61 is provided'with a cover 11 which sheds any black liquor falling downwardly from the conical bottom 34, above it. See Fig. 5. The screw69 is mounted on a hollow sleeve 18, which is mounted on a shaft 19. Steam may be admitted to the sleeve 'I8 through a rotary steam joint 30. Steam admitted through the joint 8U passes into the sleeve and from thence is diffused through the perforations into the pulp within the conveyor trough 61. The conveyor is driven by means of a variable speed motor 8|, and-a suitable train of gearing A32.

The upwardly inclined conveyor'trough 6l is provided with 'a discharge outlet 83, which communicates with the trough 8d of a horizontally disposed screw conveyor. The trough vthi cornmunicates with the upper end of the housing l2, and is provided with perforations 88, rso that liquor separated from the pulp in the horizontal conveyor may drain into the housing 12. The horizontal conveyor is provided with a tapered screw 81, which gradually increases in diameter :from its connection to the inclined conveyor to- 'ward the discharge end. The screw 8l is driven by means of a shaft 88, having mounted thereon or'surrounding which, is a perforated sleeve 89. lSteamadn'iitted through the sleeve Vv89, as already described, is diiiused into the pulp being handled by the conveyor. Connected to the lowerv half'of the housing, or trough 84, isa housing 9 I, similar to the housing 12, for the'inclined conveyor, and which connects to an opening into thehousing 12. The housing 9|, is'joined to the 'trough 84, above the perforations 86, as shown in Fig. 10, whereby to forni apressure-tight structure. The shaft 88 is driven by a variable speed motor 92, similarl 'to the motor 8|, through suitable gearing 93.

The'trough 84 of the horizontal Vconveyor discharges through van opening into a' receptacle 94, in position tol be picked up by a vertically disposed conveyor which conveys it upwardly. The receptacle k911 is` provided 'with a perforated bottom and drains'into 'the housing 9|. The'vertically disposed `'conveyor is provided with a tapered screw 97 similar to the screws described in con- 'nectionwith the other conveyors and increases in diameter from the lower to the upper discharge end. 'Surrounding the screw 97 is aperforated jacket 99 through which liquor is discharged into a surrounding imperforate housing IGI 'and passes downwardly through a lateral conduit IGS vinto the housing 9|.

The housing IlI is joined at its upper end at |62 with a fluid tight connection to the jacket Q9. The pulp is finally discharged from the upper end ofthe vertical conveyor through a discharge opening |83, from whence it may be conveyed in any suitable 'manner for'further processing as is well understood. The vertical conveyor, 'similarly to the upwardly inclined and horizontal conveyors, is driven by a separate variable speed motor Itli, through suitable gearing |06.

All of 'theliquor removed from the pulp in my vkimproved .blow tank, drains downwardly into the storage tank I.

The latteris provided with a heating coil |87, supplied with steam from any suitable source through a connection |08. The liquor is thus maintained in a'free flowing, non viscous condition. Condensate is removed from the coil ID'I through a trap |89. Liquor drained into the storage tank I4 is removed by means of a pump II I, which discharges through a conduit |I-2. A strainer IIIl is preferably interposed be- 'tween the tank Iand the pump I I I. As is well understood, the black liquor is then filtered and evaporated downto the proper density for burning.

`opening Ya valve II4 in the conduit II3 and closing a valve II5 in the conduit II2, black liquor is delivered to the manifold 5I and is discharged 6 through the nozzles 83 and 66 against the'inner and outer sides `of the inner shell 33.

The manifold 5I is provided with a steam supply through a steam supply conduit I I6, whereby steam may be employed -with the black liquor,.or alone, in cleaning out the system. At the upper end of the manifold 5|, I provide a valve II 1, connected to a conduit IIB, which leads to the connection 29, on the manifold 28. VA check valve I `I 9 adjacent the connection 29 prevents the blowing back of steam when the digestor is being discharged into the blow tank. Black liquor from the conduit II3, together with steam from the lconduit IIS may be admitted into the vmanifold v5I through the valve I I4 and from thence through the conduit IIS and perforations 3| to clean the baiiles 25 as 'already described.

V`From the foregoing description, theoperation 'of my improved apparatus will be readily understood. The contents of the digester I0, at'th'eend of a cook, and consisting of black liquor under pressure, with the batch of chips, lis vblown through the blow line 'II into the cyclone I2 where the steam is separated from the liquor and pulp and passes out through the discharge conduit 2l. Any pulp in the steam is separated out -by means of thebailies 2S in the baiile chamber 2d. The black liquor andpulppass downwardly with a whirling motion through the trap valves 22 and 23 into the inner shell 33 where it is evenly distributed about the shell. The black liquor passes out through the screened, perforated lower end of the inner shell vand drains downwardly into the storage tank I4. When the inner shell is full, above the perforations, steam accumulates above the mass and aids invforcing the black liquorV out through the perforations.

IThe pulp settles by `gravity into the lower end of the conical bottom .3!3, and passes into the lower end of the upwardly inclined conveyor trough 87, and is conveyed upwardly therefrom by the tapered conveyor screw and is discharged into the horizontal conveyor trough 8d. From thence it is conveyed horizontally to the vertical conveyor housing Aand is then carried upwardly to be discharged through the discharge chute |33. In its passage through the conveyors, saturated steam ata temperature of from 250 to 280 F. is diffused through the pulp by. means ofthe .perforated sleeves Vsurrounding the shafts so Athat it is maintained in a heated condition lat vall times and the black liquor with its lresins and .lignins is forced out therefrom through the perforated 'troughs of the conveyors. The speed of the contion. l'Ihe steam diifused through the pulpisfin part condensed, providing a small amount "of liquid which aids the steam pressure inforcing the black liquor and suspended solids from the pulp. Iny my improved method there isino foaming in theseparation of 4the liquor due to the'absence of added water and agitation. I thus avoid the addition of anti-foaming agents 'which weaken the fiber and are expensive. In actual practice I have found that black liquor after separating from the pulp in accordance with my invention hereinbefore described and with all necessary wash water added has a specific 'gravity of from 13 to 18 Be. as'compared with a specic gravity of from 3 to 7 B. when separated by `priorart methods. It thus 'requires'raround 40per'ce`nt`less heat to evaporate it down to a consistency suitable for burning and recovery of the chemicals therein.

The inner surfaces of the perforated troughs 61, 84 and 91 may be provided with finely perforated linings |20 to further aid in retaining the pulp in the troughs while being operated upon by the conveyors.

From the foregoing, it will be apparent that I have devised an improved apparatus for the separation of cooking liquor from pulp in the manufacture of paper in which the cooking liquor is separated with a minimum of dilution.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited but that it is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

l. A pulp and cooking liquor blow pit assembly comprising an inner compartment having a perforated, screen-covered wall portion with an inverted conical bottom section having a pulp and liquor discharge outlet at its bottoni, means to feed cooking liquor and pulp into the upper end of said compartment, an outer shell spaced away from and enclosing at least the perforated portion of said compartment, a tapered screw conveyor having its inlet positioned to receive liquor-soaked pulp from said discharge outlet and its conveying screw increasing in diameter from the inlet to discharge end, said conveyor extending through the outer shell for removing such pulp from the conical bottom discharge outlet to exterior of the outer shell, said conveyor having a perforated trough and a housing at least under the trough for receiving liquor draining through the latter, said trough communicating with the interior of the outer shell so that the liquor draining into the trough flows into the inside of the outer shell.

2. Apparatus as defined in claim 1 together with steam distributing means within the conveyor to diffuse steam through the pulp as the cooking liquor is being lseparated therefrom.

3. Apparatus of the character described comprising an inner vessel having a conical screened bottom with a pulp discharge outlet in the bottom, means to discharge cooking liquor and pulp into the upper end of the inner vessel, an outer shell surrounding the inner vessel, spray nozzles disposed around the outside and inside of the inner vessel, steam and liquor connections to the spray nozzles, a screw conveyor extending through the outer shell for removing pulp from the discharge opening, a closed housing for the conveyor outside the outer shell and draining into the outer shell, a second screw conveyor disposed to receive the pulp from the first mentioned conveyor, a closed housing for the second conveyor draining into the first mentioned housing, a tapered screw for each of said conveyors increasing in diameter from inlet to discharge end, a perforated trough for each of said screws, means to inject steam into the pulp during its travel through said troughs, and a separate means to drive said conveyors at selected speeds.

4. In a paper mill, a blow tank assembly comprising an inner vessel having a conical screened bottom with a pulp discharge outlet in the bottom, means to discharge cooking liquor and pulp into the upper end of the inner vessel, an

outer shell surrounding the inner vessel, a plurality of screw conveyors arranged in series. the rst of said conveyors being disposed to re-` move pulp from the lower end of the inner vessel and to discharge it outside the outer shell and the succeeding conveyors to receive the pulp outside the outer shell and finally discharge it, a tapered screw for each of said conveyors increasing in diameter from inlet to discharge end, a perforated trough for each of said conveyors, means to diffuse steam through the pulp while intransit in said conveyors, communicating housings for the conveyors draining into the outer shell, and a separate means to drive the conveyors at selected speeds.

5. Apparatus as defined in claim 4 in which the means to diffuse steam through the pulp comprises a hollow perforated conveyor shaft with a steam connection at its outer end.

6. In a blow pit assembly, a screened bottom, a pulp discharge outlet in said bottom, a plurality of screw conveyors arranged in a series leading from said bottom discharge outlet with the latter feeding into the inlet of the first of the conveyors, each of said screw conveyors including a perforated trough, each of said screw conveyors having a significant increase in diameter from its inlet to discharge end, means for driving said screw conveyors at individually selected speeds and means for diffusing steam through the pulp in and along each of said screw conveyors.

7. In a blow pit assembly, a conical screened bottom, a pulp discharge outlet in said bottom, a plurality of screw conveyors arranged in a series leading from said bottom discharge outlet with the latter feeding into the inlet of the first of the conveyors, each of said screw conveyors including a perforated trough, each of said screw conveyors having a significant increase in diameter from itsinlet to discharge end, means for driving said screw conveyors at individually selected speeds, the screw in each of said screw conveyors having a hollow shaft perforated within and along the conveyor, and means for injecting steam into each of said shafts.

8. In a blow pit assembly, a conical bottom, a pulp discharge outlet in said bottom, a plurality of screw conveyors arranged in a series leading from said bottom discharge outlet with the latter feeding into the inlet of the first of the conveyors, each of said screw conveyors including a perforated trough, each of said screw conveyors having a significant increase in diameter from its inlet to discharge end, separate means for driving each of said screw conveyors at individually selected speeds, the screw in each of said screw conveyors having a hollow shaft perforated within and along the conveyor, and means for injecting steam into each of said shafts at the larger diameter ends of said screws.

9. A pulp and cooking liquor blow tank assembly comprising a cylindrical compartment for receiving a mixture of pulp and cooking liquor and having a perforated, screen-covered wall portion with an inverted conical bottom section, an outer shell spaced away from and surrounding at least the perforated portion of said compartment, a storage tank communieating with, and positioned below, said outer shell and for receiving liquor draining through the perforated, screen portion, a screw conveyor having its inlet end positioned for receiving liquor soaked pulp from the bottom of said compartment to remove said pulp therefrom and having the'diameter of its screw progressively increasing from the inlet to discharge end and including a perforated trough so arranged that liquor draining out of the pulp ilows into the interior of the outer shell and the storage tank, and meansto remove cooking liquor from the tank.

.10. Apparatus for separating pulp from cool:- ing liquor, in the manufacture of paper, comprising a `,blow tank having an inlet permitting the entry of a mixture of pulp and cooking liquor into it and having an inverted conical lower end sufficiently permeable to allow liquor to drain through it and yet to hold back liquorsoaked pulp, a screw conveyor having its inlet end positioned to receive such pulp from the lower end of the blow tank and the diameter of the screw progressively increasing from the inlet to the discharge end of the conveyor, al

perforated trough for the conveyor screw to revolve in and for liquor to drain through the perforations, and a steam distributor within the conveyor to diffuse steam through the plup along the conveyor and its trough, the perforations in the trough being located at least in its lower part and under at least some part of the conveyor screw.

11. In combination with a blow pit having a pulp discharge outlet at its bottom, a tapered screw conveyor comprising a conveyor screw and a trough for the screw to rotate in and having its inlet communicating with the blow pit discharge outlet, perforations at least in the lower part of the trough and under at least part of the screw, the screw and its said trough having a signicantly greater diameter at their discharge end than at the inlet end and increasing in diameter from the inlet to the discharge end, and means for diffusing steam through the pulp in and along said conveyor screw.

PAUL G. VON HIIDEBRANDT.

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